Bottom Line:
Articular cartilage lesions are a common pathology of the knee joint, and many patients may benefit from cartilage repair surgeries that offer the chance to avoid the development of osteoarthritis or delay its progression.This goal is best fulfilled by magnetic resonance imaging (MRI).In the third section, a short overview is provided on the regulatory issues of the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) regarding MR follow-up studies of patients after cartilage repair surgeries.

Affiliation: MR Centre - High Field MR, Department of Radiology, Medical University of Vienna, Vienna, Austria.

ABSTRACTArticular cartilage lesions are a common pathology of the knee joint, and many patients may benefit from cartilage repair surgeries that offer the chance to avoid the development of osteoarthritis or delay its progression. Cartilage repair surgery, no matter the technique, requires a noninvasive, standardized, and high-quality longitudinal method to assess the structure of the repair tissue. This goal is best fulfilled by magnetic resonance imaging (MRI). The present article provides an overview of the current state of the art of MRI of cartilage repair. In the first 2 sections, preclinical and clinical MRI of cartilage repair tissue are described with a focus on morphological depiction of cartilage and the use of functional (biochemical) MR methodologies for the visualization of the ultrastructure of cartilage repair. In the third section, a short overview is provided on the regulatory issues of the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) regarding MR follow-up studies of patients after cartilage repair surgeries.

Mentions:
Several technical details regarding T2 mapping have also been described, including the importance of the stimulated echo contribution that can factitiously elevate T2 values, requiring modification of slice profile to produce more robust T2 measurements.123 The measurement errors associated with stimulated echo may be avoided by ignoring the first echo acquired in multiecho acquisitions when calculating T2 or by measuring T2 with a series of single echo acquisitions. More efficient T2 data acquisition has been demonstrated with the use of a DESS sequence that has comparable results with the standard multiecho spin-echo T2.124 However, as with other mapping measurements, the greater the number of data sets, that is, TE values for T2, the greater the accuracy of the T2 measurements. T2 assessment of repair tissue has been described at 1.5-T, 3-T, and 7-T whole body systems as well as high-field (8.5 T) microscopy systems studying repair (Fig. 6).73,118,125-129 Despite the technical challenges of the thinner cartilage of the ankle joint, T2 and T2* assessment of MACT and native cartilage have been described.130

Mentions:
Several technical details regarding T2 mapping have also been described, including the importance of the stimulated echo contribution that can factitiously elevate T2 values, requiring modification of slice profile to produce more robust T2 measurements.123 The measurement errors associated with stimulated echo may be avoided by ignoring the first echo acquired in multiecho acquisitions when calculating T2 or by measuring T2 with a series of single echo acquisitions. More efficient T2 data acquisition has been demonstrated with the use of a DESS sequence that has comparable results with the standard multiecho spin-echo T2.124 However, as with other mapping measurements, the greater the number of data sets, that is, TE values for T2, the greater the accuracy of the T2 measurements. T2 assessment of repair tissue has been described at 1.5-T, 3-T, and 7-T whole body systems as well as high-field (8.5 T) microscopy systems studying repair (Fig. 6).73,118,125-129 Despite the technical challenges of the thinner cartilage of the ankle joint, T2 and T2* assessment of MACT and native cartilage have been described.130

Bottom Line:
Articular cartilage lesions are a common pathology of the knee joint, and many patients may benefit from cartilage repair surgeries that offer the chance to avoid the development of osteoarthritis or delay its progression.This goal is best fulfilled by magnetic resonance imaging (MRI).In the third section, a short overview is provided on the regulatory issues of the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) regarding MR follow-up studies of patients after cartilage repair surgeries.

Affiliation:
MR Centre - High Field MR, Department of Radiology, Medical University of Vienna, Vienna, Austria.

ABSTRACTArticular cartilage lesions are a common pathology of the knee joint, and many patients may benefit from cartilage repair surgeries that offer the chance to avoid the development of osteoarthritis or delay its progression. Cartilage repair surgery, no matter the technique, requires a noninvasive, standardized, and high-quality longitudinal method to assess the structure of the repair tissue. This goal is best fulfilled by magnetic resonance imaging (MRI). The present article provides an overview of the current state of the art of MRI of cartilage repair. In the first 2 sections, preclinical and clinical MRI of cartilage repair tissue are described with a focus on morphological depiction of cartilage and the use of functional (biochemical) MR methodologies for the visualization of the ultrastructure of cartilage repair. In the third section, a short overview is provided on the regulatory issues of the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) regarding MR follow-up studies of patients after cartilage repair surgeries.